We have a well that is fed by spring water. The cistern is comprised of three tiles stacked on each other. They are about 4 feet tall each. Where the bottom tile and the 2nd tile connect, I have roots growing in. This in turn has caused me to loose quite a bit of water and we keep running out of water. This happened a couple of years ago to the upper tiles and we had to dig down on the outside to kill the weeds and then used a special concrete that hardens quickly and withstands water to seal the inside. It looks like we may not have sealed very well at the bottom tile area. Now my question. Do we have to dig down on the outside again (this is mainly root and rocks - took about 3 hours to dig less than 1 1/2 feet last time ). Is there a root killer that we can apply to the joints on the inside to kill the roots that will be safe for us? Should I just scrape the roots from the inside and then seal really well or what? If we have to dig down, I am afraid that we will have to hire a heavey equipment to come in because of how hard the ground is. I am hoping that I can scrape the roots on the inside and then apply a root killer (that is safe for us) and then seal well. Anyone have experience with this before???? Thanks in advance!!!!!!!!!!!!